Process for the preparation of a tetraalkylcyclobutane-1,3-diol using a promoted nickel-based catalyst

ABSTRACT

The present invention relates to the production of a 2,2,4,4-tetraalkylcyclobutane-1,3-diol. In one embodiment, the present invention relates to the production of a 2,2,4,4-tetraalkylcyclobutane-1,3-diol by hydrogenation of a 2,2,4,4-tetraalkylcyclobutane-1,3-dione in the presence of a promoted nickel-based catalyst.

CROSS REFERENCES TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. § 119(e) to U.S.Provisional Application Ser. No. 60/872,319 filed on Dec. 2, 2006, whichis hereby incorporated by reference.

DESCRIPTION OF THE INVENTION

1. Field of the Invention

The present disclosure relates to the production of a2,2,4,4-tetraalkylcyclobutane-1,3-diol. In one embodiment, the presentinvention relates to the production of a2,2,4,4-tetraalkylcyclobutane-1,3-diol by hydrogenation of a2,2,4,4-tetraalkylcyclobutane-1,3-dione in the presence of a promotednickel-based catalyst.

2. Background of the Invention

2,2,4,4-Tetramethylcyclobutane-1,3-diol is an important intermediate forproducing a variety of polymeric materials having advantageousproperties. For example, polyesters derived from dicarboxylic acids and2,2,4,4-tetramethylcyclobutane-1,3-diol can possess higher glasstransition temperatures, superior weatherability, and/or improvedhydrolytic stability compared to polyesters prepared from othercommonly-used, polyester forming diols. A2,2,4,4-tetramethylcyclobutane-1,3-diol of Formula I is typicallyproduced by the catalytic hydrogenation of the corresponding2,2,4,4-tetramethylcyclobutane-1,3-dione as shown below.

Typically, the hydrogenation of 2,2,4,4-tetramethylcyclobutane-1,3-dioneproduces the corresponding 2,2,4,4-tetramethylcyclobutane-1,3-diol as amixture of cis and trans isomers. It would be desirable to produce2,2,4,4-tetramethylcyclobutane-1,3-diol with a specific cis:trans isomerratio in order to control glass transition temperatures and/orcrystallization rates in copolyesters.

SUMMARY OF THE INVENTION

The present disclosure relates to the production of a2,2,4,4-tetraalkylcyclobutane-1,3-diol. In one embodiment, the presentinvention relates to the production of a2,2,4,4-tetraalkylcyclobutane-1,3-diol by hydrogenation of a2,2,4,4-tetraalkylcyclobutane-1,3-dione in the presence of a promotednickel-based catalyst.

In one embodiment, the present invention relates to a process forproducing a 2,2,4,4-tetraalkylcyclobutane-1,3-diol, comprisingcontacting a 2,2,4,4-tetraalkylcyclobutane-1,3-dione with hydrogen inthe presence of a promoted nickel-based catalyst under conditions oftemperature and pressure sufficient to form a2,2,4,4-tetraalkylcyclobutane-1,3-diol, wherein the alkyl radicals eachindependently have 1 to 8 carbon atoms.

In one embodiment, the present invention relates to a process forproducing 2,2,4,4-tetramethylcyclobutane-1,3-diol, comprising contacting2,2,4,4-tetramethylcyclobutane-1,3-dione, a promoted nickel-basedcatalyst, a non-protic solvent, and hydrogen in a hydrogenation zoneunder conditions of temperature and pressure sufficient to form2,2,4,4-tetramethylcyclobutane-1,3-diol.

In one embodiment, the present invention relates to a processcomprising: (1) feeding isobutyric anhydride to a pyrolysis zone,wherein the isobutyric anhydride is heated at a temperature of 350° C.to 600° C. to produce a vapor effluent comprising dimethylketene,isobutyric acid, and unreacted isobutyric anhydride; (2) cooling thevapor effluent to condense isobutyric acid and isobutyric anhydride andseparating the condensate from the dimethylketene vapor; (3) feeding thedimethylketene vapor to an absorption zone, wherein the dimethylketenevapor is contacted with and dissolved in a solvent comprising an estercontaining 4 to 20 carbon atoms and consisting of residues of analiphatic carboxylic acid and an alkanol to produce an absorption zoneeffluent comprising a solution of dimethylketene in the solvent; (4)feeding the absorption zone effluent to a dimerization zone wherein theabsorption zone effluent is heated at a temperature ranging from 70° C.to 140° C. to convert dimethylketene to2,2,4,4-tetramethylcyclobutane-1,3-dione to produce a dimerization zoneeffluent comprising a solution of2,2,4,4-tetramethylcyclobutane-1,3-dione in the solvent; and (5)contacting the 2,2,4,4-tetramethylcyclobutane-1,3-dione with hydrogen inthe presence of a promoted nickel-based catalyst under conditions oftemperature and pressure sufficient to form a2,2,4,4-tetramethylcyclobutane-1,3-diol.

Additional objects and advantages of the invention will be set forth inpart in the description which follows, and in part will be obvious fromthe description, or may be learned by practice of the invention. Theobjects and advantages of the invention will be realized and attained bymeans of the elements and combinations particularly pointed out in theappended claims.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory onlyand are not restrictive of the invention, as claimed.

DETAILED DESCRIPTION OF THE INVENTION

The present disclosure may be understood more readily by reference tothe following detailed description of certain embodiments of theinvention and the working examples.

In accordance with the purpose of this invention, certain embodiments ofthe invention are described in the Summary of the Invention and arefurther described herein below. Also, other embodiments of the inventionare described herein.

The term “promoted nickel-based catalyst” refers to a nickel-basedcatalyst that has been promoted by a promoter compound. The nickel-basedcatalyst is promoted by contacting the catalyst with a solution of apromoter compound under appropriate conditions. Appropriate promotingconditions are exemplified, but not limited to, the methods in theexamples below. Other conventional methods of applying promoters tocatalysts are well-known to those of skill in the art. Applicants makeno representation regarding the nature of the interaction of thepromoter compound and the nickel-based catalyst, but instead contemplateas within the scope of the present invention all promoted nickel-basedcatalysts that are active in the claimed processes. In one embodiment,the yield of the hydrogenation reaction is greater than 10%, forexample, greater than 40%, for example, greater than 50%, for example,greater than 60%, for example, greater than 70%, for example, greaterthan 80%, for example, greater than 90%.

The terms “Group 4 of the Periodic Table,” or “Group 4,” and “Group 4metal” refer to the subgroup numbering system adopted by theInternational union of Pure and Applied Chemistry in 1984, and refer tothe elements of Group 4 of the Periodic Table, i.e., Group 4 refers totitanium, zirconium, and hafnium. The term “Group 4 metal” includes, forexample and without limitation, the zero valent metal, the metal inionic form, and the metal in an alloy.

The term nickel-based catalyst refers to a catalyst comprising nickelincluding, for example and without limitation, zero valent nickel,nickel in an ionic form, and nickel in an alloy.

Unless otherwise indicated, all numbers expressing quantities ofingredients, properties such as molecular weight, reaction conditions,and so forth used in the specification and claims are to be understoodas being modified in all instances by the term “about.” Accordingly,unless indicated to the contrary, the numerical parameters set forth inthe following specification and attached claims are approximations thatmay vary depending upon the desired properties sought to be obtained bythe present invention. At the very least, each numerical parametershould at least be construed in light of the number of reportedsignificant digits and by applying ordinary rounding techniques.Further, the ranges stated in this disclosure and the claims areintended to include the entire range specifically and not just theendpoint(s). For example, a range stated to be 0 to 10 is intended todisclose all whole numbers between 0 and 10 such as, for example, 1, 2,3, 4, etc., as well as the endpoints 0 and 10. Also, a range associatedwith chemical substituent groups such as, for example, “C₁ to C₅hydrocarbons,” is intended to specifically include and disclose C₁ andC₅ hydrocarbons as well as C₂, C₃, and C₄ hydrocarbons.

Notwithstanding that the numerical ranges and parameters setting forththe broad scope of the invention are approximations, the numericalvalues set forth in the specific examples are reported as precisely aspossible. Any numerical value, however, inherently contains certainerrors necessarily resulting from the standard deviation found in theirrespective testing measurements.

As used in the specification and the appended claims, the singular forms“a,” “an,” and “the” include their plural referents unless the contextclearly dictates otherwise. For example, reference to the processing ormaking of a “catalyst,” or a “promoter,” is intended to include theprocessing or making of a plurality of catalysts, or promoters.References to a composition containing or including “a” promoter or “a”catalyst is intended to include other promoters or other catalysts,respectively, in addition to the one named.

By “comprising” or “containing” or “including” we mean that at least thenamed compound, element, particle, or method step, etc., is present inthe composition or article or method, but we do not exclude the presenceof other compounds, catalysts, materials, particles, method steps, etc.,even if the other such compounds, materials, particles, method steps,etc., have the same function as what is named, unless expressly excludedin the claims.

It is also to be understood that the mention of one or more method stepsdoes not preclude the presence of additional method steps before orafter the combined recited steps or intervening method steps betweenthose steps expressly identified. Moreover, the lettering of processsteps or ingredients is a convenient means for identifying discreteactivities or ingredients and it is to be understood that the recitedlettering can be arranged in any sequence, unless otherwise indicated.

In one embodiment, the present invention provides processes for making a2,2,4,4-tetraalkylcyclobutane-1,3-diol by hydrogenation of a2,2,4,4-tetraalkylcyclobutane-1,3-dione. In a general embodiment, theinvention provides processes for making a2,2,4,4-tetraalkylcyclobutane-1,3-diol comprising contacting a2,2,4,4-tetraalkylcyclobutane-1,3-dione with hydrogen in the presence ofa nickel-based catalyst promoted with a Group 1 metal, a Group 4 metal,a Group 8 metal, a Group 10 metal, or a Group 11 metal underhydrogenation conditions of temperature and pressure sufficient to formthe 2,2,4,4-tetraalkylcyclobutane-1,3-diol.

In another general embodiment, the invention provides a process formaking a 2,2,4,4-tetraalkylcyclobutane-1,3-diol comprising contacting a2,2,4,4-tetraalkylcyclobutane-1,3-dione with hydrogen in the presence ofa cesium-promoted nickel-based catalyst under hydrogenation conditionsof temperature and pressure sufficient to form the2,2,4,4-tetraalkylcyclobutane-1,3-diol. In another general embodiment,the invention provides a process for making a2,2,4,4-tetraalkylcyclobutane-1,3-diol comprising contacting a2,2,4,4-tetraalkylcyclobutane-1,3-dione with hydrogen in the presence ofa copper-promoted nickel-based catalyst under hydrogenation conditionsof temperature and pressure sufficient to form the2,2,4,4-tetraalkylcyclobutane-1,3-diol. In another general embodiment,the invention provides a process for making a2,2,4,4-tetraalkylcyclobutane-1,3-diol comprising contacting a2,2,4,4-tetraalkylcyclobutane-1,3-dione with hydrogen in the presence ofa platinum-promoted nickel-based catalyst under hydrogenation conditionsof temperature and pressure sufficient to form the2,2,4,4-tetraalkylcyclobutane-1,3-diol. In another general embodiment,the invention provides a process for making a2,2,4,4-tetraalkylcyclobutane-1,3-diol comprising contacting a2,2,4,4-tetraalkylcyclobutane-1,3-dione with hydrogen in the presence ofa ruthenium-promoted nickel-based catalyst under hydrogenationconditions of temperature and pressure sufficient to form the2,2,4,4-tetraalkylcyclobutane-1,3-diol. In another general embodiment,the invention provides a process for making a2,2,4,4-tetraalkylcyclobutane-1,3-diol comprising contacting a2,2,4,4-tetraalkylcyclobutane-1,3-dione with hydrogen in the presence ofa zirconium-promoted nickel-based catalyst under hydrogenationconditions of temperature and pressure sufficient to form the2,2,4,4-tetraalkylcyclobutane-1,3-diol. In one embodiment, the presentinvention is useful for the preparation of2,2,4,4-tetramethylcyclobutane-1,3-diol from2,2,4,4-tetramethylcyclobutane-1,3-dione.

The hydrogenation reaction of 2,2,4,4-tetraalkylcyclobutane-1,3-dione toproduce a 2,2,4,4-tetraalkylcyclobutane-1,3-diol of Formula II is shownbelow:

wherein R₁, R₂, R₃, and R₄ each independently represent an alkylradical, for example, a lower alkyl radical having 1 to 8 carbon atoms.The alkyl radicals may be linear, branched, or a combination of linearand branched alkyl radicals. The2,2,4,4-tetraalkylcyclobutane-1,3-dione, for example,2,2,4,4-tetramethylcyclobutane-1,3-dione, is hydrogenated to thecorresponding 2,2,4,4-tetraalkylcyclobutane-1,3-diol, for example,2,2,4,4-tetramethylcyclobutane-1,3-diol, in accordance with the presentprocesses.

In one embodiment, the alkyl radicals R₁, R₂, R₃, and R₄ on the2,2,4,4-tetraalkylcyclobutane-1,3-dione each independently have 1 to 8carbon atoms. Other 2,2,4,4-tetraalkylcyclobutane-1,3-diones that aresuitably reduced to the corresponding diols include, but are not limitedto, 2,2,4,4-tetraethylcyclobutane-1,3-dione,2,2,4,4-tetra-n-propylcyclobutane-1,3-dione,2,2,4,4-tetra-n-butylcyclobutane-1,3-dione,2,2,4,4-tetra-n-pentylcyclobutane-1,3-dione,2,2,4,4-tetra-n-hexylcyclobutane-1,3-dione,2,2,4,4-tetra-n-heptylcyclobutane-1,3-dione,2,2,4,4-tetra-n-octylcyclobutane-1,3-dione,2,2-dimethyl-4,4-diethylcyclobutane-1,3-dione,2-ethyl-2,4,4-trimethylcyclobutane-1,3-dione,2,4-dimethyl-2,4-diethyl-cyclobutane-1,3-dione,2,4-dimethyl-2,4-di-n-propylcyclobutane-1,3-dione,2,4-n-dibutyl-2,4-diethylcyclobutane-1,3-dione,2,4-dimethyl-2,4-diisobutylcyclobutane-1,3-dione, and2,4-diethyl-2,4-diisoamylcyclobutane-1,3-dione.

In other embodiments, the alkyl radicals R₁, R₂, R₃, and R₄ on the2,2,4,4-tetraalkylcyclobutane-1,3-dione each independently have 1 to 6carbon atoms, or 1 to 5 carbon atoms, or 1 to 4 carbon atoms, or 1 to 3carbon atoms, or 1 to 2 carbon atoms. In another embodiment, the alkylradicals R₁, R₂, R₃, and R₄ on the2,2,4,4-tetraalkylcyclobutane-1,3-dione each have 1 carbon atom.

In one embodiment, the promoter compound comprises a Group 4 metal.

The compounds used as promoter compounds include, but are not limitedto, water soluble compounds. Such compounds include, but are not limitedto, their oxides, hydroxides, and alkoxides, and the corresponding saltssuch as acetates, carbonates, phosphates, and nitrates.

The amount of the promoter compound on the catalyst depends upon thepromoting conditions. In one embodiment, the amount of the promotercompound on the catalyst ranges from 0.01 to 10 weight percent(abbreviated herein as “wt %”) based upon the total weight of thecatalyst. For example, certain processes of the present invention use anickel-based catalyst promoted with a promoter compound comprising 0.01to 10 weight percent (wt %) of the promoter compound, based on the totalweight of the promoted nickel-based catalyst. Other examples of thepromoter compound levels on the promoted nickel-based catalyst are 0.05to 7 wt % of the promoter compound and 1 to 5 wt % of the promotercompound, based on the total weight of the promoted nickel-basedcatalyst. In one embodiment, the nickel-based catalyst comprises 1 wt %to 95 wt % nickel, or 1 wt % to 80 wt % nickel, or 50 wt % to 80 wt %nickel, or 60 wt % to 80 wt % nickel, based on the total weight of thecatalyst.

In one embodiment, the nickel-based catalyst is promoted with a Group 4metal, for example, zirconium. The amount of the zirconium compound thatmay be incorporated by the nickel-based catalyst depends upon thepromoting conditions but, for example, may range from 0.01 to 10 weightpercent (abbreviated herein as “wt %”) based upon the total weight ofthe promoted nickel-based catalyst. For example, in some embodiments,the processes of the present invention may use a nickel-based catalystpromoted with zirconium comprising 0.01 to 10 weight percent (wt %)zirconium, based on the total weight of the promoted nickel-basedcatalyst. Other examples of zirconium promoting levels on the promotednickel-based catalyst are 0.05 to 7 wt % zirconium and 1 to 5 wt %zirconium.

Suitable supports for the promoted nickel-based catalysts include, butare not limited to, silica, alumina, aluminosilicate, silica/alumina,kieselguhr, titania, graphite, silicon carbide, carbon, zirconia,chromate, barium chromate, zinc oxide, clay, and alumina-clay. Suitableforms of the support include powder, extrudate, spheres, or pellets.

The hydrogenation conditions of pressure and temperature may be varieddepending on the activity of the catalyst, the mode of operation,selectivity considerations, and the desired rate of conversion. Theprocesses typically are conducted at temperatures in the range of 75° C.to 250° C. The processes typically are conducted at pressures in therange of 689 kPa (100 psi) (7 bar) to 41,368 kPa (6000 psi) (420 bar).Further examples of temperatures and/or pressures at which the processesof the invention may be operated are 120° C. to 200° C. at 1380 kPa (200psi) (14 bar) to 20,684 kPa (3000 psi) (207 bar), and 130° C. to 180° C.at 2068 kPa (300 psi) (21 bar) to 14,789 kPa (2000 psi) (140 bar). Whilerates and conversions generally increase with increasing pressure, theenergy costs for compression of hydrogen, as well as the increased costof high-pressure equipment generally make advantageous the use of thelowest pressure practical. For certain embodiments of the presentinvention, the hydrogenation process has a temperature ranging from 130°C. to 140° C. and a pressure ranging from 3450 kPa (500 psi) (34.5 barg)to 10000 kPa (1450 psi) (100 barg). For certain embodiments of thepresent invention, the hydrogenation process has a temperature rangingfrom 160° C. to 170° C. and a pressure ranging from 3450 kPa (500 psi)(34.5 barg) to 10000 kPa (1450 psi) (100 barg).

For certain embodiments of the present invention, the hydrogenationprocess has a temperature range chosen from 75° C. to 250° C., 80° C. to250° C., 90° C. to 250° C., 100° C. to 250° C., 110° C. to 250° C., 120°C. to 250° C., 130° C. to 250° C., 140° C. to 250° C., 150° C. to 250°C., 160° C. to 250° C., 170° C. to 250° C., 180° C. to 250° C., 190° C.to 250° C., 200° C. to 250° C., 210° C. to 250° C., 220° C. to 250° C.,230° C. to 250° C., or 240° C. to 250° C. For certain embodiments of thepresent invention, the hydrogenation process has a temperature rangechosen from 75° C. to 240° C., 80° C. to 240° C., 90° C. to 240° C.,100° C. to 240° C., 110° C. to 240° C., 120° C. to 240° C., 130° C. to240° C., 140° C. to 240° C., 150° C. to 240° C., 160° C. to 240° C.,170° C. to 240° C., 180° C. to 240° C., 190° C. to 240° C., 200° C. to240° C., 210° C. to 240° C., 220° C. to 240° C., or 230° C. to 240° C.For certain embodiments of the present invention, the hydrogenationprocess has a temperature range chosen from 75° C. to 230° C., 80° C. to230° C., 90° C. to 230° C., 100° C. to 230° C., 110° C. to 230° C., 120°C. to 230° C., 130° C. to 230° C., 140° C. to 230° C., 150° C. to 230°C., 160° C. to 230° C., 170° C. to 230° C., 180° C. to 230° C., 190° C.to 230° C., 200° C. to 230° C., 210° C. to 230° C., or 220° C. to 230°C.

For certain embodiments of the present invention, the hydrogenationprocess has a temperature range chosen from 75° C. to 220° C., 80° C. to220° C., 90° C. to 220° C., 100° C. to 220° C., 110° C. to 220° C., 120°C. to 220° C., 130° C. to 220° C., 140° C. to 220° C., 150° C. to 220°C., 160° C. to 220° C., 170° C. to 220° C., 180° C. to 220° C., 190° C.to 220° C., 200° C. to 220° C., or 210° C. to 220° C. For certainembodiments of the present invention, the hydrogenation process has atemperature range chosen from 75° C. to 210° C., 80° C. to 210° C., 90°C. to 210° C., 100° C. to 210° C., 110° C. to 210° C., 120° C. to 210°C., 130° C. to 210° C., 140° C. to 210° C., 150° C. to 210° C., 160° C.to 210° C., 170° C. to 210° C., 180° C. to 210° C., 190° C. to 210° C.,or 200° C. to 210° C. For certain embodiments of the present invention,the hydrogenation process has a temperature range chosen from 75° C. to200° C., 80° C. to 200° C., 90° C. to 200° C., 100° C. to 200° C., 110°C. to 200° C., 120° C. to 200° C., 130° C. to 200° C., 140° C. to 200°C., 150° C. to 200° C., 160° C. to 200° C., 170° C. to 200° C., 180° C.to 200° C., or 190° C. to 200° C.

For certain embodiments of the present invention, the hydrogenationprocess has a temperature range chosen from 75° C. to 190° C., 80° C. to190° C., 90° C. to 190° C., 100° C. to 190° C., 110° C. to 190° C., 120°C. to 190° C., 130° C. to 190° C., 140° C. to 190° C., 150° C. to 190°C., 160° C. to 190° C., 170° C. to 190° C., or 180° C. to 190° C. Forcertain embodiments of the present invention, the hydrogenation processhas a temperature range chosen from 75° C. to 180° C., 80° C. to 180°C., 90° C. to 180° C., 100° C. to 180° C., 110° C. to 180° C., 120° C.to 180° C., 130° C. to 180° C., 140° C. to 180° C., 150° C. to 180° C.,160° C. to 180° C., or 170° C. to 180° C. For certain embodiments of thepresent invention, the hydrogenation process has a temperature rangechosen from 75° C. to 170° C., 80° C. to 170° C., 90° C. to 170° C.,100° C. to 170° C., 110° C. to 170° C., 120° C. to 170° C., 130° C. to170° C., 140° C. to 170° C., 150° C. to 170° C., or 160° C. to 170° C.

For certain embodiments of the present invention, the hydrogenationprocess has a temperature range chosen from 75° C. to 160° C., 80° C. to160° C., 90° C. to 160° C., 100° C. to 160° C., 110° C. to 160° C., 120°C. to 160° C., 130° C. to 160° C., 140° C. to 160° C., or 150° C. to160° C. For certain embodiments of the present invention, thehydrogenation process has a temperature range chosen from 75° C. to 150°C., 80° C. to 150° C., 90° C. to 150° C., 100° C. to 150° C., 110° C. to150° C., 120° C. to 150° C., 130° C. to 150° C., or 140° C. to 150° C.For certain embodiments of the present invention, the hydrogenationprocess has a temperature range chosen from 75° C. to 140° C., 80° C. to140° C., 90° C. to 140° C., 100° C. to 140° C., 110° C. to 140° C., 120°C. to 140° C., or 130° C. to 140° C. For certain embodiments of thepresent invention, the hydrogenation process has a temperature rangechosen from 75° C. to 130° C., 80° C. to 130° C., 90° C. to 130° C.,100° C. to 130° C., 110° C. to 130° C., or 120° C. to 130° C.

For certain embodiments of the present invention, the hydrogenationprocess has a temperature range chosen from 75° C. to 120° C., 80° C. to120° C., 90° C. to 120° C., 100° C. to 120° C., or 110° C. to 120° C.For certain embodiments of the present invention, the hydrogenationprocess has a temperature range chosen from 75° C. to 110° C., 80° C. to110° C., 90° C. to 110° C., or 100° C. to 110° C. For certainembodiments of the present invention, the hydrogenation process has atemperature range chosen from 75° C. to 100° C., 80° C. to 100° C., or90° C. to 100° C. For certain embodiments of the present invention, thehydrogenation process has a temperature range chosen from 75° C. to 90°C., or 80° C. to 90° C. For certain embodiments of the presentinvention, the hydrogenation process has a temperature range chosen from75° C. to 80° C.

For certain embodiments of the present invention, the hydrogenationprocess has a pressure range chosen from 100 psi to 6000 psi, 200 psi to6000 psi, 300 psi to 6000 psi, 400 psi to 6000 psi, 500 psi to 6000 psi,1000 psi to 6000 psi, 1500 psi to 6000 psi, 2000 psi to 6000 psi, 2500psi to 6000 psi, 3000 psi to 6000 psi, 3500 psi to 6000 psi, 4000 psi to6000 psi, 4500 psi to 6000 psi, 5000 psi to 6000 psi, or 5500 psi to6000 psi. For certain embodiments of the present invention, thehydrogenation process has a pressure range chosen from 100 psi to 5500psi, 200 psi to 5500 psi, 300 psi to 5500 psi, 400 psi to 5500 psi, 500psi to 5500 psi, 1000 psi to 5500 psi, 1500 psi to 5500 psi, 2000 psi to5500 psi, 2500 psi to 5500 psi, 3000 psi to 5500 psi, 3500 psi to 5500psi, 4000 psi to 5500 psi, 4500 psi to 5500 psi, or 5000 psi to 5500psi.

For certain embodiments of the present invention, the hydrogenationprocess has a pressure range chosen from 100 psi to 5000 psi, 200 psi to5000 psi, 300 psi to 5000 psi, 400 psi to 5000 psi, 500 psi to 5000 psi,1000 psi to 5000 psi, 1500 psi to 5000 psi, 2000 psi to 5000 psi, 2500psi to 5000 psi, 3000 psi to 5000 psi, 3500 psi to 5000 psi, 4000 psi to5000 psi, or 4500 psi to 5000 psi. For certain embodiments of thepresent invention, the hydrogenation process has a pressure range chosenfrom 100 psi to 4500 psi, 200 psi to 4500 psi, 300 psi to 4500 psi, 400psi to 4500 psi, 500 psi to 4500 psi, 1000 psi to 4500 psi, 1500 psi to4500 psi, 2000 psi to 4500 psi, 2500 psi to 4500 psi, 3000 psi to 4500psi, 3500 psi to 4500 psi, or 4000 psi to 4500 psi. For certainembodiments of the present invention, the hydrogenation process has apressure range chosen from 100 psi to 4000 psi, 200 psi to 4000 psi, 300psi to 4000 psi, 400 psi to 4000 psi, 500 psi to 4000 psi, 1000 psi to4000 psi, 1500 psi to 4000 psi, 2000 psi to 4000 psi, 2500 psi to 4000psi, 3000 psi to 4000 psi, or 3500 psi to 4000 psi.

For certain embodiments of the present invention, the hydrogenationprocess has a pressure range chosen from 100 psi to 3500 psi, 200 psi to3500 psi, 300 psi to 3500 psi, 400 psi to 3500 psi, 500 psi to 3500 psi,1000 psi to 3500 psi, 1500 psi to 3500 psi, 2000 psi to 3500 psi, 2500psi to 3500 psi, or 3000 psi to 3500 psi. For certain embodiments of thepresent invention, the hydrogenation process has a pressure range chosenfrom 100 psi to 3000 psi, 200 psi to 3000 psi, 300 psi to 3000 psi, 400psi to 3000 psi, 500 psi to 3000 psi, 1000 psi to 3000 psi, 1500 psi to3000 psi, 2000 psi to 3000 psi, or 2500 psi to 3000 psi. For certainembodiments of the present invention, the hydrogenation process has apressure range chosen from 100 psi to 2500 psi, 200 psi to 2500 psi, 300psi to 2500 psi, 400 psi to 2500 psi, 500 psi to 2500 psi, 1000 psi to2500 psi, 1500 psi to 2500 psi, 2000 psi to 2500 psi.

For certain embodiments of the present invention, the hydrogenationprocess has a pressure range chosen from 100 psi to 2000 psi, 200 psi to2000 psi, 300 psi to 2000 psi, 400 psi to 2000 psi, 500 psi to 2000 psi,1000 psi to 2000 psi, or 1500 psi to 2000 psi. For certain embodimentsof the present invention, the hydrogenation process has a pressure rangechosen from 100 psi to 1500 200 psi to 1500 psi, 300 psi to 1500 psi,400 psi to 1500 psi, 500 psi to 1500 psi, or 1000 psi to 1500 psi. Forcertain embodiments of the present invention, the hydrogenation processhas a pressure range chosen from 100 psi to 1000 psi, 200 psi to 1000psi, 300 psi to 1000 psi, 400 psi to 1000 psi, or 500 psi to 1000 psi.

For certain embodiments of the present invention, the hydrogenationprocess has a pressure range chosen from 100 psi to 500 psi, 200 psi to500 psi, 300 psi to 500 psi, or 400 psi to 500 psi. For certainembodiments of the present invention, the hydrogenation process has apressure range chosen from 100 psi to 400 psi, 200 psi to 400 psi, or300 psi to 400 psi. For certain embodiments of the present invention,the hydrogenation process has a pressure range chosen from 100 psi to300 psi, or 200 psi to 300 psi. For certain embodiments of the presentinvention, the hydrogenation process has a pressure range chosen from100 psi to 200 psi.

It is contemplated that the processes of the invention can be carriedout at least one of the temperature ranges disclosed herein and at leastone of the pressure ranges disclosed herein.

The source and purity of the hydrogen gas used in the processes of thepresent invention are not critical. The hydrogen gas used in theprocesses may comprise fresh hydrogen or a mixture of fresh hydrogen andrecycled hydrogen. The hydrogen gas can be a mixture of hydrogen and,optionally, minor amounts, typically less than 30 mole %, of componentssuch as CO and CO₂, and inert gases, such as argon, nitrogen, ormethane. Typically, the hydrogen gas comprises at least 70 mole % ofhydrogen. For example, the hydrogen gas comprises at least 90 mole % or,in another example, at least 97 mole %, of hydrogen. The hydrogen gasmay be obtained from any of the conventional sources well known in theart such as, for example, by partial oxidation or steam reforming ofnatural gas. Pressure swing absorption can be used if a high purityhydrogen gas is desired. If hydrogen gas recycle is utilized in one ofthe processes, then the recycle hydrogen gas may contain minor amountsof one or more products of the hydrogenation reaction which have notbeen fully condensed in the product recovery stage downstream from thehydrogenation zone.

The hydrogenation of 2,2,4,4-tetraalkylcyclobutane-1,3-dione typicallyproduces cis-2,2,4,4-tetraalkylcyclobutane-1,3-diol andtrans-2,2,4,4-tetraalkylcyclobutane-1,3-diol. In certain embodiments ofthe present invention, the cis/trans molar ratio ranges from 1.2 to 0.4or 1.1 to 0.4 or 1.0 to 0.4 or 0.9 to 0.4 or 0.8 to 0.4 or 0.7 to 0.4 or0.6 to 0.4 or 0.5 to 0.4. In certain embodiments of the presentinvention, the cis/trans molar ratio ranges from 1.2 to 0.5 or 1.1 to0.5 or 1.0 to 0.5 or 0.9 to 0.5 or 0.8 to 0.5 or 0.7 to 0.5 or 0.6 to0.5. In certain embodiments of the present invention, the cis/transmolar ratio ranges from 1.2 to 0.6 or 1.1 to 0.6 or 1.0 to 0.6 or 0.9 to0.6 or 0.8 to 0.6 or 0.7 to 0.6. In certain embodiments of the presentinvention, the cis/trans molar ratio ranges from 1.2 to 0.7 or 1.1 to0.7 or 1.0 to 0.7 or 0.9 to 0.7 or 0.8 to 0.7. In certain embodiments ofthe present invention, the cis/trans molar ratio ranges from 1.2 to 0.8or 1.1 to 0.8 or 1.0 to 0.8 or 0.9 to 0.8. In certain embodiments of thepresent invention, the cis/trans molar ratio ranges from 1.2 to 0.9 or1.1 to 0.9 or 1.0 to 0.9. In certain embodiments of the presentinvention, the cis/trans molar ratio ranges from 1.2 to 1.0 or 1.1 to1.0. In certain embodiments of the present invention, the cis/transmolar ratio ranges from 1.2 to 1.1.

The processes of this invention may be carried out in the absence orpresence of a solvent, e.g., a solvent for the2,2,4,4-tetraalkylcyclobutane-1,3-dione being hydrogenated which iscompatible with the catalyst and the hydrogenation product or products.Examples of such solvents include alcohols such as methanol and ethanol;ethers, such as dimethyl ether and diethyl ether; glycols such as mono-,di- and tri-ethylene glycol; glycol ethers, such as ethylene glycolmonobutyl ether and diethylene glycol monobutyl ether; saturatedhydrocarbons such as hexane, cyclohexane, octane, and decane; andesters, such as isopropyl isobutyrate, isobutyl propionate, octylacetate, isobutyl isobutyrate, isobutyl acetate, and the like. In oneembodiment, the solvent is isobutyl isobutyrate. In one embodiment, the2,2,4,4-tetraalkylcyclobutane-1,3-dione is dissolved in the solvent at aconcentration of 1 to 60% (w/w), for example 5 to 50%, or 10 to 25%. Inone embodiment in which the solvent is isobutyl isobutyrate, the2,2,4,4-tetraalkylcyclobutane-1,3-dione is dissolved in the solvent at aconcentration of 1 to 60% (w/w), for example 5 to 50%, or 10 to 25%. Incertain embodiments the process is conducted in the absence of solventand use the neat, molten 2,2,4,4-tetraalkylcyclobutane-1,3-dione aloneor as a mixture with the 2,2,4,4-tetraalkylcyclobutane-1,3-diol andother hydrogenation products, including1-hydroxy-2,2,4-trimethyl-3-pentanone,3-hydroxy-2,2,4,4,-tetramethylcyclobutane-1-one, and2,2,4-trimethyl-1,3-pentanediol, as the feed to the process.

Another embodiment of the present invention is drawn to a process toproduce a 2,2,4,4-tetraalkylcyclobutane-1,3-diol comprising (1) feedingisobutyric anhydride to a pyrolysis zone to produce a vapor effluentcomprising dimethylketene, isobutyric acid, and unreacted isobutyricanhydride; (2) cooling the vapor effluent to condense isobutyric acidand isobutyric anhydride and separating the condensate from thedimethylketene vapor; (3) feeding the dimethylketene vapor to anabsorption zone wherein the dimethylketene vapor is dissolved in asolvent comprising an ester containing 4 to 20 carbon atoms andconsisting of residues of an aliphatic carboxylic acid and an alkanol toproduce an absorption zone effluent comprising a solution ofdimethylketene in the solvent; (4) feeding the absorption zone effluentto a dimerization zone wherein the absorption zone effluent is heated toconvert dimethylketene to 2,2,4,4-tetramethylcyclobutane-1,3-dione toproduce a dimerization zone effluent comprising a solution of2,2,4,4-tetramethylcyclobutane-1,3-dione in the solvent; and (5)contacting the 2,2,4,4-tetraalkylcyclobutane-1,3-dione with hydrogen inthe presence of a promoted nickel-based catalyst under conditions oftemperature and pressure sufficient to form a2,2,4,4-tetraalkylcyclobutane-1,3-diol.

Another embodiment of the present invention is drawn to a process toproduce a 2,2,4,4-tetraalkylcyclobutane-1,3-diol comprising (1) feedinga dialkyl carboxylic acid to a pyrolysis zone wherein the dialkylcarboxylic acid produces a vapor effluent comprising dialkylketene,water, and unreacted dialkyl carboxylic acid; (2) cooling the vaporeffluent to condense water and dialkyl carboxylic acid and separatingthe condensate from the dialkylketene vapor; (3) feeding thedialkylketene vapor to an absorption zone wherein the dialkylketenevapor is dissolved in a solvent comprising an ester containing 4 to 20carbon atoms and consisting of residues of an aliphatic carboxylic acidand an alkanol to produce an absorption zone effluent comprising asolution of dialkylketene in the solvent; (4) feeding the absorptionzone effluent to a dimerization zone wherein the absorption zoneeffluent is heated to convert dialkylketene to2,2,4,4-tetraalkylcyclobutane-1,3-dione to produce a dimerizationeffluent comprising a solution of2,2,4,4-tetraalkylcyclobutane-1,3-dione in the solvent; and (5)contacting the tetraalkylcyclobutane-1,3-dione with hydrogen in thepresence of a promoted nickel-based catalyst under conditions oftemperature and pressure sufficient to form a2,2,4,4-tetraalkylcyclobutane-1,3-diol.

The nature of the process for making the dialkylketene is not criticaland any conventional method may be used, including, but not limited to,the methods disclosed in U.S. Pat. Nos. 1,602,699, 2,160,841, 2,202,046,2,278,537, 2,806,064, 3,201,474, 3,259,469, 3,366,689, 3,403,181,5,475,144 and 6,232,504, all of which are incorporated herein byreference for their disclosure of processes for making a dialkylketene.Processes for the preparation of ketenes, for example, dimethylketene,and cyclobutane-1,3-diones, for example,2,2,4,4-tetramethylcyclobutane-1,3-dione, may be combined with allaspects of the present invention related to preparation of the2,2,4,4-tetraalkylcyclobutane-1,3-diols, including mixtures of cis andtrans-2,2,4,4-tetraalkylcyclobutane-1,3-diols.

All of these novel processes may be carried out as a batch,semi-continuous, or continuous process and may utilize a variety ofreactor types. Examples of suitable reactor types include, but are notlimited to, stirred tank, continuous stirred tank, slurry, tubular,fixed bed, and trickle bed. The term “continuous” as used herein means aprocess wherein reactants are introduced and products withdrawnsimultaneously in an uninterrupted manner. By “continuous” it is meantthat the process is substantially or completely continuous in operation,in contrast to a “batch” process. “Continuous” is not meant in any wayto prohibit normal interruptions in the continuity of the process dueto, for example, start-up, reactor maintenance, or scheduled shut downperiods. The term “batch” process as used herein means a process whereinall the reactants are added to the reactor and then processed accordingto a predetermined course of reaction during which essentially nomaterial is fed into or removed from the reactor. For example, in abatch operation, a slurry of the catalyst in the cyclobutanedione and/ora solvent in which the cyclobutanedione has been dissolved is fed to apressure vessel equipped with means for agitation. The pressure vesselis then pressurized with hydrogen to a predetermined pressure followedby heating to bring the reaction mixture to the desired temperature.After the hydrogenation is complete, the reaction mixture is removedfrom the pressure vessel, the catalyst is separated by filtration, andthe 2,2,4,4-tetramethylcyclobutane-1,3-diol product is isolated, forexample, in a distillation train or by crystallization. The term“semicontinuous” means a process where some of the reactants are chargedat the beginning of the process and the remaining reactants are fedcontinuously as the reaction progresses. Alternatively, a semicontinuousprocess may also include a process similar to a batch process in whichall the reactants are added at the beginning of the process except thatone or more of the products are removed continuously as the reactionprogresses.

The process may be operated as a continuous process, althoughsemi-continuous and batch processes, all of which processes are withinthe scope of the invention. Continuous operation may utilize a fixed bedwith a larger particle size of catalyst such as, for example, granules,pellets, various multilobal shaped pellets, rings, or saddles that arewell known to skilled persons in the art. As an example of a continuousprocess, the catalyst bed may be fixed in a high pressure, tubular orcolumnar reactor and the liquid 2,2,4,4-tetraalkylcyclobutane-1,3-dione,dissolved in a solvent if necessary or desired, fed continuously intothe top of the bed at elevated pressure and temperature, and the crudehydrogenation product removed from the base of the reactor.Alternatively, it is possible to feed the2,2,4,4-tetraalkylcyclobutane-1,3-dione into the bottom of the bed andremove the crude product from the top of the reactor. It is alsopossible to use two or more catalyst beds or hydrogenation zonesconnected in parallel or in series to improve conversion, to reduce thequantity of catalyst, or to bypass a catalyst bed for periodicmaintenance or catalyst removal. Another mode of continuous operationutilizes a slurry of the catalyst in an agitated pressure vessel, whichis equipped with a filter leg to permit continuous removal of a solutionof product in unreacted 2,2,4,4-tetraalkylcyclobutane-1,3-dione and/or asolvent. In this manner, a liquid reactant or reactant solution can becontinuously fed to, and product solution continuously removed from, anagitated pressure vessel containing an agitated slurry of the catalyst.

In one embodiment, the present invention provides processes forproducing a 2,2,4,4-tetraalkylcyclobutane-1,3-diol of Formula II,comprising contacting a 2,2,4,4-tetraalkylcyclobutane-1,3-dione withhydrogen in the presence of a promoted nickel-based catalyst underconditions of temperature and pressure sufficient to form a2,2,4,4-tetraalkylcyclobutane-1,3-diol, wherein the alkyl radicals R₁,R₂, R₃ and R₄ each independently have 1 to 8 carbon atoms.

In one embodiment, the present invention provides processes forproducing a 2,2,4,4-tetraalkylcyclobutane-1,3-diol of Formula II,comprising contacting a 2,2,4,4-tetraalkylcyclobutane-1,3-dione withhydrogen in the presence of a promoted nickel-based catalyst underconditions of temperature and pressure sufficient to form a2,2,4,4-tetraalkylcyclobutane-1,3-diol, wherein the alkyl radicals R₁,R₂, R₃ and R₄ each independently have 1 to 8 carbon atoms and whereinless than 2 mol % of the 2,2,4,4-tetraalkylcyclobutane-1,3-dione isconverted to ring-open products. By “ring-open products” it is meanthydrogenation products of a 2,2,4,4-tetraalkylcyclobutane-1,3-dionewhich do not comprise a cyclic structure. In one embodiment, 100 mol %of the 2,2,4,4-tetraalkylcyclobutane-1,3-dione is converted and lessthan 2 mol % of the 2,2,4,4-tetraalkylcyclobutane-1,3-dione is convertedto ring-open products. In one embodiment, 90 mol % of the2,2,4,4-tetraalkylcyclobutane-1,3-dione is converted and less than 2.0mol % of the 2,2,4,4-tetraalkylcyclobutane-1,3-dione is converted toring-open products. In one embodiment, 80 mol % of the2,2,4,4-tetraalkylcyclobutane-1,3-dione is converted and less than 2.0mol % of the 2,2,4,4-tetraalkylcyclobutane-1,3-dione is converted toring-open products.

In one embodiment, the present invention provides processes forproducing a 2,2,4,4-tetraalkylcyclobutane-1,3-diol of Formula II,comprising contacting a 2,2,4,4-tetraalkylcyclobutane-1,3-dione withhydrogen in the presence of a promoted nickel-based catalyst underconditions of temperature and pressure sufficient to form a2,2,4,4-tetraalkylcyclobutane-1,3-diol, wherein the alkyl radicals R₁,R₂, R₃ and R₄ each independently have 1 to 8 carbon atoms and whereinthe reaction mixture after hydrogenation comprises less than 3.5 mol %ring-open products. In one embodiment, the reaction mixture afterhydrogenation comprises less than 3.0 mol % ring-open compounds. In oneembodiment, the reaction mixture after hydrogenation comprises less than2.5 mol % ring-open products. In one embodiment, the reaction mixtureafter hydrogenation comprises less than 2.0 mol % ring-open products. Inone embodiment, the reaction mixture after hydrogenation comprises lessthan 1.5 mol % ring-open products. In one embodiment, the reactionmixture after hydrogenation comprises less than 1.0 mol % ring-openproducts. In one embodiment, the reaction mixture after hydrogenationcomprises less than 0.5 mol % ring-open products.

In one embodiment, the promoter compound comprises a Group 4 metalcompound. In one embodiment, the promoter compound comprises zirconium.In one embodiment, the source of the promoter metal is ZrO₂.

In one embodiment, the promoted nickel-based catalyst comprises 0.01 to10 weight percent (wt %) promoter compound, based on the total weight ofthe promoted nickel-based catalyst. In one embodiment, the promotednickel-based catalyst comprises 0.5 to 7 wt % promoter compound, basedon the total weight of the promoted nickel-based catalyst. In oneembodiment, the promoted nickel-based catalyst comprises 1 to 5 wt %promoter compound, based on the total weight of the promotednickel-based catalyst.

In one embodiment, the present invention provides processes forproducing a 2,2,4,4-tetraalkylcyclobutane-1,3-diol of Formula II,comprising contacting a 2,2,4,4-tetraalkylcyclobutane-1,3-dione withhydrogen in the presence of a promoted nickel-based catalyst underconditions of temperature and pressure sufficient to form a2,2,4,4-tetraalkylcyclobutane-1,3-diol. In one embodiment, the alkylradical radicals R₁, R₂, R₃ and R₄ each independently have 1 to 4 carbonatoms.

In one embodiment, the alkyl radical radicals R₁, R₂, R₃ and R₄ each aremethyl groups. In one embodiment, the2,2,4,4-tetraalkylcyclobutane-1,3-diol is2,2,4,4-tetramethylcyclobutane-1,3-diol. In one embodiment, the2,2,4,4-tetraalkylcyclobutane-1,3-dione is2,2,4,4-tetramethylcyclobutane-1,3-dione.

In one embodiment, the present invention provides processes forproducing a 2,2,4,4-tetraalkylcyclobutane-1,3-diol of Formula II,comprising contacting a 2,2,4,4-tetraalkylcyclobutane-1,3-dione withhydrogen in the presence of a promoted nickel-based catalyst underconditions of temperature and pressure sufficient to form a2,2,4,4-tetraalkylcyclobutane-1,3-diol, wherein the alkyl radicals R₁,R₂, R₃ and R₄ each independently have 1 to 8 carbon atoms and whereinthe process further comprises a non-protic solvent. In one embodiment,the non-protic solvent comprises an unsaturated hydrocarbon, anon-cyclic ester, i.e., not a lactone, or ether. The term “non-cyclicester” means the ester is not a lactone, although the alkanol oraliphatic carboxylic acid residues of the ester may have cyclic rings.In one embodiment, the non-cyclic ester contains 4 to 20 carbon atomsand comprises at least one residue of an aliphatic carboxylic acid andat least one residue of an alkanol. In one embodiment, the non-cyclicester is selected from isopropyl isobutyrate, isobutyl propionate, octylacetate, isobutyl isobutyrate, isobutyl acetate, and mixtures thereof.

In one embodiment, the present invention provides processes forproducing a 2,2,4,4-tetraalkylcyclobutane-1,3-diol of Formula II,comprising contacting a 2,2,4,4-tetraalkylcyclobutane-1,3-dione withhydrogen in the presence of a promoted nickel-based catalyst underconditions of temperature and pressure sufficient to form a2,2,4,4-tetraalkylcyclobutane-1,3-diol, wherein the alkyl radicals R₁,R₂, R₃ and R₄ each independently have 1 to 8 carbon atoms and whereinthe process further comprises a protic solvent. In one embodiment, theprotic solvent comprises one or more solvents chosen from a monohydricalcohol, a dihydric alcohol, a polyhydric alcohol, and mixtures thereof.In one embodiment, the protic solvent comprises one or more solventschosen from a monohydric alcohol, a dihydric alcohol, and mixturesthereof. In one embodiment, the protic solvent comprises methanol orethylene glycol.

In one embodiment, the present invention provides processes forproducing a 2,2,4,4-tetraalkylcyclobutane-1,3-diol of Formula II,comprising contacting a 2,2,4,4-tetraalkylcyclobutane-1,3-dione withhydrogen in the presence of a promoted nickel-based catalyst underconditions of temperature and pressure sufficient to form a2,2,4,4-tetraalkylcyclobutane-1,3-diol, wherein the alkyl radicals R₁,R₂, R₃ and R₄ each independently have 1 to 8 carbon atoms and whereinthe promoted nickel-based catalyst comprises a support. In oneembodiment, the support comprises one or more of silica, alumina,aluminosilicate, silica/alumina, kieselguhr, titania, graphite, siliconcarbide, carbon, zirconia, chromate, barium chromate, zinc oxide, clay,or alumina-clay. In one embodiment, the support comprises a formselected from powder, extrudate, spheres, and pellets.

In one embodiment, the present invention provides processes forproducing a 2,2,4,4-tetraalkylcyclobutane-1,3-diol of Formula II,comprising contacting a 2,2,4,4-tetraalkylcyclobutane-1,3-dione withhydrogen in the presence of a promoted nickel-based catalyst underconditions of temperature and pressure sufficient to form a2,2,4,4-tetraalkylcyclobutane-1,3-diol, wherein the alkyl radicals R₁,R₂, R₃ and R₄ each independently have 1 to 8 carbon atoms and whereinthe pressure ranges from 689 kPa (100 psi) to 41,368 kPa (6000 psi). Inone embodiment, the pressure ranges from 1380 kPa (200 psi) to 20,684kPa (3000 psi). In one embodiment, the pressure ranges from 2068 kPa(300 psi) to 14,789 kPa (2000 psi). In one embodiment, the temperatureranges from 75° C. to 250° C. In one embodiment, the temperature rangesfrom 120° C. to 200° C. In one embodiment, the temperature ranges from130° C. to 180° C.

In one embodiment, the present invention provides processes forproducing a 2,2,4,4-tetraalkylcyclobutane-1,3-diol of Formula II,comprising contacting a 2,2,4,4-tetraalkylcyclobutane-1,3-dione withhydrogen in the presence of a promoted nickel-based catalyst underconditions of temperature and pressure sufficient to form a2,2,4,4-tetraalkylcyclobutane-1,3-diol, wherein the alkyl radicals R₁,R₂, R₃ and R₄ each independently have 1 to 8 carbon atoms and whereinthe 2,2,4,4-tetraalkylcyclobutane-1,3-diol comprisescis-2,2,4,4-tetramethylcyclobutane-1,3-diol andtrans-2,2,4,4-tetramethylcyclobutane-1,3-diol and the2,2,4,4-tetramethylcyclobutane-1,3-diol has a cis/trans molar ratio of0.4 to 1.2. In one embodiment, the2,2,4,4-tetramethylcyclobutane-1,3-diol has a cis/trans molar ratio of0.6 to 1.0. In one embodiment, the2,2,4,4-tetramethylcyclobutane-1,3-diol has a cis/trans molar ratioranging from 0.7 to 1.0.

In one embodiment, the present invention provides processes forproducing a 2,2,4,4-tetraalkylcyclobutane-1,3-diol of Formula II,comprising contacting a 2,2,4,4-tetraalkylcyclobutane-1,3-dione withhydrogen in the presence of a promoted nickel-based catalyst underconditions of temperature and pressure sufficient to form a2,2,4,4-tetraalkylcyclobutane-1,3-diol, wherein the alkyl radicals R₁,R₂, R₃ and R₄ each independently have 1 to 8 carbon atoms and whereinthe 2,2,4,4-tetramethylcyclobutane-1,3-dione, the2,2,4,4-tetramethylcyclobutane-1,3-diol, or both are in the moltenphase.

In one embodiment, the present invention provides processes forproducing 2,2,4,4-tetramethylcyclobutane-1,3-diol, comprising contacting2,2,4,4-tetramethylcyclobutane-1,3-dione, a promoted nickel-basedcatalyst, a non-protic solvent, and hydrogen in a hydrogenation zoneunder conditions of temperature and pressure sufficient to form2,2,4,4-tetramethylcyclobutane-1,3-diol. In one such embodiment, the2,2,4,4-tetramethylcyclobutane-1,3-dione and hydrogen are continuouslyfed into the hydrogenation zone. In one such embodiment, thehydrogenation zone has a temperature ranging from 75° C. to 250° C. Inone such embodiment, the pressure ranges from 689 kPa (100 psi) to41,368 kPa (6000 psi).

In one embodiment, the present invention provides processes forproducing 2,2,4,4-tetramethylcyclobutane-1,3-diol, comprising contacting2,2,4,4-tetramethylcyclobutane-1,3-dione, a promoted nickel-basedcatalyst, a non-protic solvent, and hydrogen in a hydrogenation zoneunder conditions of temperature and pressure sufficient to form2,2,4,4-tetramethylcyclobutane-1,3-diol, and further comprisingcontinuously recovering an effluent comprising the2,2,4,4-tetramethylcyclobutane-1,3-diol and the solvent from thehydrogenation zone. In one such embodiment, the process furthercomprises continuously recycling a portion of the effluent to thehydrogenation zone. In one such embodiment, the process furthercomprises continuously recovering the effluent from the hydrogenationzone and recovering at least a portion of the2,2,4,4-tetramethylcyclobutane-1,3-diol from the effluent to form adepleted 2,2,4,4-tetramethylcyclobutane-1,3-diol stream. In one suchembodiment, at least a portion of the depleted2,2,4,4-tetramethylcyclobutane-1,3-diol stream is recycled to thehydrogenation zone. In one such embodiment, the hydrogenation zonecomprises a tubular, fixed bed, or trickle bed reactor. In one suchembodiment, the hydrogenation zone comprises a stirred tank, acontinuous stirred tank, or a slurry reactor. In one such embodiment,the 2,2,4,4-tetramethylcyclobutane-1,3-diol has a cis/trans molar ratioof 1.2 or less. In one such embodiment, the2,2,4,4-tetramethylcyclobutane-1,3-diol has a cis/trans molar ratio of0.4 or more.

In one embodiment, the present invention provides processes forproducing 2,2,4,4-tetramethylcyclobutane-1,3-diol comprising (1) feedingisobutyric anhydride to a pyrolysis zone, wherein the isobutyricanhydride is heated at a temperature of 350° C. to 600° C. to produce avapor effluent comprising dimethylketene, isobutyric acid, and unreactedisobutyric anhydride; (2) cooling the vapor effluent to condenseisobutyric acid and isobutyric anhydride and separating the condensatefrom the dimethylketene vapor; (3) feeding the dimethylketene vapor toan absorption zone, wherein the dimethylketene vapor is contacted withand dissolved in a solvent comprising an ester containing 4 to 20 carbonatoms and consisting of residues of an aliphatic carboxylic acid and analkanol to produce an absorption zone effluent comprising a solution ofdimethylketene in the solvent; (4) feeding the absorption zone effluentto a dimerization zone wherein the absorption zone effluent is heated ata temperature ranging from 70 to 140° C. to convert dimethylketene to2,2,4,4-tetramethylcyclobutane-1,3-dione to produce a dimerization zoneeffluent comprising a solution of2,2,4,4-tetramethylcyclobutane-1,3-dione in the solvent; and (5)contacting the 2,2,4,4-tetramethylcyclobutane-1,3-dione with hydrogen inthe presence of a promoted nickel-based catalyst under conditions oftemperature and pressure sufficient to form a2,2,4,4-tetramethylcyclobutane-1,3-diol.

In one embodiment, the present invention provides processes for making2,2,4,4-tetramethylcyclobutane-1,3-diol comprising continuously feeding2,2,4,4-tetramethylcyclobutane-1,3-dione, a non-protic solvent, andhydrogen to a hydrogenation zone comprising a promoted nickel-basedcatalyst at pressure of 689 kPa (100 psi) (7 bar) to 41,368 kPa (6000psi) (420 bar) and a hydrogenation temperature of 75 to 250° C. andcontinuously recovering from said hydrogenation zone an effluentcomprising 2,2,4,4-tetramethylcyclobutane-1,3-diol and the non-proticsolvent. In another embodiment, the process may further comprisecontinuously recycling a portion of the effluent to the hydrogenationzone. The hydrogenation zone may be any suitable reactor type including,but not limited to, stirred tank, continuous stirred tank, slurry,tubular, fixed bed, and trickle bed. For example, the processes of theinvention may be carried out in a trickle bed reactor operated in theliquid phase. Certain embodiments of the invention are further describedand illustrated by the following examples.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the scope or spirit of the invention. Otherembodiments of the invention will be apparent to those skilled in theart from consideration of the specification and practice of theinvention disclosed herein.

It is intended that the specification and examples be considered asexemplary only, with a true scope and spirit of the invention beingindicated by the following claims.

Further embodiments of the invention include:

A process for producing a 2,2,4,4-tetraalkylcyclobutane-1,3-diol ofFormula II, comprising contacting a2,2,4,4-tetraalkylcyclobutane-1,3-dione with hydrogen in the presence ofa promoted nickel-based catalyst under conditions of temperature andpressure sufficient to form a 2,2,4,4-tetraalkylcyclobutane-1,3-diol,

wherein each of the alkyl radicals R₁, R₂, R₃ and R₄ has, independentlyfrom each other, 1 to 8 carbon atoms.

The process according to the embodiment in paragraph 71, furthercomprising contacting a nickel-based catalyst with a promoter to formthe promoted nickel-based catalyst.

The process according to any of the embodiments in paragraphs 71-72,wherein the promoted nickel-based catalyst comprises a promoter metalchosen from a Group 4 metal.

The process according to any of the embodiments in paragraphs 71-73,wherein the promoter comprises zirconium.

The process according to any of the embodiments in paragraphs 71-74,wherein the promoted nickel-based catalyst comprises 0.01 to 10 weightpercent (wt %) promoter metal, based on the total weight of the promotednickel-based catalyst.

The process according to any of the embodiments in paragraphs 71-75,wherein the promoted nickel-based catalyst comprises 0.5 to 7 wt %promoter.

The process according to any of the embodiments in paragraphs 71-76,wherein the promoted nickel-based catalyst comprises 1 to 5 wt %promoter.

The process according to any of the embodiments in paragraphs 71-77,wherein each of the alkyl radical radicals R₁, R₂, R₃, and R₄ has,independently from each other, 1 to 4 carbon atoms.

The process according to any of the embodiments in paragraphs 71-78,wherein each alkyl radical R₁, R₂, R₃, and R₄ is a methyl group.

The process according to any of the embodiments in paragraphs 71-79,wherein the 2,2,4,4-tetraalkylcyclobutane-1,3-dione is2,2,4,4-tetramethylcyclobutane-1,3-dione.

The process according to any of the embodiments in paragraphs 71-80,wherein a non-protic solvent comprising an unsaturated hydrocarbon, anon-cyclic ester, or an ether, is present during the formation of the2,2,4,4-tetraalkylcyclobutane-1,3-diol.

The process according to any of the embodiments in paragraphs 71-82,wherein the non-cyclic ester contains 4 to 20 carbon atoms and comprisesat least one residue of an aliphatic carboxylic acid and at least oneresidue of an alkanol.

The process according to any of the embodiments in paragraphs 71-82,wherein the non-cyclic ester is chosen from isopropyl isobutyrate,isobutyl propionate, octyl acetate, isobutyl isobutyrate, isobutylacetate, and mixtures thereof.

The process according to any of the embodiments in paragraphs 71-83,wherein a protic solvent comprising one or more solvents chosen from amonohydric alcohol, a dihydric alcohol, a polyhydric alcohol, andmixtures thereof is present during the formation of the2,2,4,4-tetraalkylcyclobutane-1,3-diol.

The process according to any of the embodiments in paragraphs 71-84,wherein the protic solvent comprises methanol and ethylene glycol.

The process according to any of the embodiments in paragraphs 71-85,wherein the promoted nickel-based catalyst comprises a support, andwherein the support comprises one or more of silica, alumina,aluminosilicate, silica/alumina, kieselguhr, titania, graphite, siliconcarbide, carbon, zirconia, chromate, barium chromate, zinc oxide, clay,and alumina-clay.

The process according to any of the embodiments in paragraphs 71-86,wherein the support comprises a form chosen from powder, extrudate,spheres, and pellets.

The process according to any of the embodiments in paragraphs 71-87,wherein the pressure is from 100 psi to 6000 psi.

The process according to any of the embodiments in paragraphs 71-88,wherein the pressure is from 1380 kPa (200 psi) to 20,684 kPa (3000psi).

The process according to any of the embodiments in paragraphs 71-89,wherein the pressure is from 300 psi to 2000 psi.

The process according to any of the embodiments in paragraphs 71-90,wherein the temperature is from 75° C. to 250° C.

The process according to any of the embodiments in paragraphs 71-91,wherein the temperature is from 120° C. to 200° C.

The process according to any of the embodiments in paragraphs 71-92,wherein the temperature is from 130° C. to 180° C.

The process according to any of the embodiments in paragraphs 71-93,wherein the 2,2,4,4-tetraalkylcyclobutane-1,3-diol comprisescis-2,2,4,4-tetramethylcyclobutane-1,3-diol andtrans-2,2,4,4-tetramethylcyclobutane-1,3-diol and the2,2,4,4-tetramethylcyclobutane-1,3-diol has a cis/trans molar ratio of0.4 to 1.2.

The process according to any of the embodiments in paragraphs 71-94,wherein the 2,2,4,4-tetramethylcyclobutane-1,3-diol has a cis/transmolar ratio of 0.6 to 1.0.

The process according to any of the embodiments in paragraphs 71-95,wherein the 2,2,4,4-tetramethylcyclobutane-1,3-diol has a cis/transmolar ratio of 0.7 to 1.0.

The process according to any of the applicable embodiments in paragraphs71-96, wherein the process is a continuous, semi-batch, or batchprocess.

The process according to any of the embodiments in paragraphs 71-97,wherein the 2,2,4,4-tetramethylcyclobutane-1,3-dione, the2,2,4,4-tetramethylcyclobutane-1,3-diol, or both are in the liquidphase.

A process for producing 2,2,4,4-tetramethylcyclobutane-1,3-diol,comprising contacting 2,2,4,4-tetramethylcyclobutane-1,3-dione, apromoted nickel-based catalyst, a non-protic solvent, and hydrogen in ahydrogenation zone under conditions of temperature and pressuresufficient to form 2,2,4,4-tetramethylcyclobutane-1,3-diol.

The process according to any of the embodiments in the paragraph 99,wherein the 2,2,4,4-tetramethylcyclobutane-1,3-dione and hydrogen arecontinuously fed into the hydrogenation zone.

The process according to any of the embodiments in paragraphs 99-100,wherein the hydrogenation zone has a temperature from 75° C. to 250° C.

The process according to any of the embodiments in paragraphs 99-101,wherein the pressure is from 100 psi to 6000 psi.

The process according to any of the embodiments in paragraphs 99-102,further comprising continuously recovering an effluent comprising the2,2,4,4-tetramethylcyclobutane-1,3-diol and the solvent from thehydrogenation zone.

The process according to any of the embodiments in paragraphs 99-103,further comprising continuously recycling a portion of the effluent tothe hydrogenation zone.

The process according to any of the embodiments in paragraphs 99-104,further comprising continuously recovering the effluent from thehydrogenation zone and recovering at least a portion of the2,2,4,4-tetramethylcyclobutane-1,3-diol from the effluent to form adepleted diol stream.

The process according to any of the embodiments in paragraphs 99-105,wherein at least a portion of the depleted diol stream is recycled tothe hydrogenation zone.

The process according to any of the embodiments in paragraphs 99-106,wherein the hydrogenation zone comprises a tubular reactor, a fixed bedreactor, trickle bed reactor, stirred tank reactor, continuous stirredtank reactor, or slurry reactor.

The process according to any of the embodiments in paragraphs 99-107,wherein the 2,2,4,4-tetramethylcyclobutane-1,3-diol has a cis/transmolar ratio of 1.2 or less.

The process according to any of the embodiments in paragraphs 99-108,wherein the 2,2,4,4-tetramethylcyclobutane-1,3-diol has a cis/transmolar ratio of 0.4 or more.

The process according to any of the embodiments in paragraphs 99-109,wherein the 2,2,4,4-tetramethylcyclobutane-1,3-diol has a cis/transmolar ratio of 0.7 to 1.0.

A process for producing 2,2,4,4-tetramethylcyclobutane-1,3-diolcomprising:

-   -   (a) feeding isobutyric anhydride to a pyrolysis zone, wherein        the isobutyric anhydride is heated at a temperature of 350° C.        to 600° C. to produce a vapor effluent comprising        dimethylketene, isobutyric acid, and unreacted isobutyric        anhydride;    -   (b) cooling the vapor effluent to condense isobutyric acid and        isobutyric anhydride and separating the condensate from the        dimethylketene vapor;    -   (c) feeding the dimethylketene vapor to an absorption zone,        wherein the dimethylketene vapor is contacted with a solvent        comprising an ester containing 4 to 20 carbon atoms to produce        an effluent comprising a solution of dimethylketene in the        solvent; wherein the ester comprises residues of an aliphatic        carboxylic acid and an alkanol;    -   (d) feeding the absorption zone effluent to a dimerization zone        wherein the absorption zone effluent is heated at a temperature        of from 70° C. to 140° C. to convert dimethylketene to        2,2,4,4-tetramethylcyclobutane-1,3-dione to produce a        dimerization zone effluent comprising a solution of        2,2,4,4-tetramethylcyclobutane-1,3-dione in the solvent; and    -   (e) contacting the 2,2,4,4-tetramethylcyclobutane-1,3-dione with        hydrogen in the presence of a promoted nickel-based catalyst        under conditions of temperature and pressure sufficient to form        a 2,2,4,4-tetramethylcyclobutane-1,3-diol.

EXAMPLES

The following examples illustrate in general the processes of thepresent invention for the production of2,2,4,4-tetraalkylcyclobutane-1,3-diols by hydrogenation of2,2,4,4-tetraalkylcyclobutane-1,3-dione.

General

The following is a general description of the reactor system, catalystpreparation, hydrogenation process, and analytical methods usedhenceforward in the Examples described below unless otherwise specified.

30.2 g of 2,2,4,4-tetramethylcyclobutane-1,3-dione, 1.0 g of a catalyst(either promoted or non-promoted, as necessary), and 171 g of isobutylisobutyrate were charged into a 300 ml autoclave fitted with a magneticstirrer, nitrogen gas purge, cooling coil, and temperature-controlledheater. The autoclave was sealed, purged with nitrogen, pressurized to32 bar (6,200 kPa) of hydrogen, and heated to 160° C. After stirring themixture for 3 hr at 160° C., the solution was cooled and the pressurewas released. The catalyst was removed by hot filtration. The filtrateproduct samples were analyzed by capillary GLC analysis as follows:

The filtrate product samples were heated to 100° C. 20-25 drops of theliquid sample were transferred to a 2 ml autoinjector vial, which wasthen filled to the 1 ml mark with DMSO. The samples were analyzed bycapillary gas-liquid chromatography (“GC”) using an Agilent Model 6890Gas Chromatograph with an FID detector. The GC samples were injectedonto a 0.25 μm (30 m×0.5 mm) DB Wax fused silica capillary column. Foreach analysis, the initial temperature of the column was set at 5° C.,held for 4 minutes, ramped to 125° C. at a rate of 12° C./min, held for5 minutes, ramped to 165° C. at a rate of 3° C./min, then ramped to 240°C. at a rate of 15° C./min and held for 5 minutes at 240° C. Results aregiven as area percentages, normalized for isobutyl isobutyrate.

The following abbreviations apply throughout the working examples andtables:

TMCB 2,2,4,4-tetramethylcyclobutane-1,3-dione Ring-open1-hydroxy-2,2,4-trimethyl-3-pentanone Ketol (a product of the partialhydrogenation and ring opening of 2,2,4,4-tetramethylcyclobutane-1,3-dione) Cyclic Ketol 3-hydroxy-2,2,4,4-tetramethylcyclobutanone (aproduct of the partial hydrogenation of 2,2,4,4-tetramethylcyclobutane-1,3-dione) TMPD 2,2,4-trimethyl-1,3-pentanediol(a product of the hydrogenation of Ring-opened Ketol) Cis-Diolcis-2,2,4,4-tetramethylcyclobutane-1,3-diol Trans-Dioltrans-2,2,4,4-tetramethylcyclobutane-1,3-diol

The conversion, selectivity, and yield of the hydrogenation process aswell as the cis:trans ratio of the2,2,4,4-tetramethylcyclobutane-1,3-diol product were calculated on thebasis of GC area percentages using the following formulas:

${{Conversion}\mspace{14mu} \%} = {\frac{\left( {{moles}\mspace{14mu} T\; M\; C\; B\mspace{14mu} {fed}} \right) - \left( {{moles}\mspace{14mu} T\; M\; C\; B\mspace{14mu} {remaining}} \right)}{\left( {{moles}\mspace{14mu} T\; M\; C\; B\mspace{14mu} {fed}} \right)} \times 100}$${{Yield}\mspace{14mu} \%} = {\frac{\left( {{moles}\mspace{14mu} {Cis}\text{-}{Diol}} \right) + \left( {{moles}\mspace{14mu} {Trans}\text{-}{Diol}} \right)}{\left( {{moles}\mspace{14mu} T\; M\; C\; B\mspace{14mu} {fed}} \right)} \times 100}$${Selectivity} = {\frac{\left( {{moles}\mspace{14mu} {Cis}\text{-}{Diol}} \right) + \left( {{moles}\mspace{14mu} {Trans}\text{-}{Diol}} \right)}{\left( {{moles}\mspace{14mu} T\; M\; C\; B\mspace{14mu} {fed}} \right) - \left( {{moles}\mspace{14mu} T\; M\; C\; B\mspace{11mu} {remaining}} \right)} = \frac{Yield}{Conversion}}$${{{Cis}/{Trans}}\mspace{14mu} {Ratio}} = \frac{\left( {{moles}\mspace{14mu} {Cis}\text{-}{Diol}} \right)}{\left( {{moles}\mspace{14mu} {Trans}\text{-}{Diol}} \right)}$

Comparative Example 1

2,2,4,4-Tetramethylcyclobutane-1,3-dione was hydrogenated in thepresence of a G-96B-RS 62% nickel on kieselguhr catalyst from Süd-Chemieusing the general procedure described previously.

The results of the hydrogenation of TMCB using the G-96B-RS 62% nickelon kieselguhr catalyst are shown in Table 1.

TABLE 1 Hydrogenation of 2,2,4,4-tetramethylcyclobutane- 1,3-dione usingG-96B-RS 62% nickel on kieselguhr catalyst. Comparative Example 1 MetalNi Promoter none Support kieselguhr Temperature 160° C. Pressure 32 barTMCB % 0 Ring-Open 2.5 Ketol % Cyclic Ketol % 1.1 TMPD % 1.4 Cis-Diol %39.0 Trans-Diol % 54.0 Conversion % 100 Selectivity % 94.8 Yield % 94.8Cis/Trans 0.7

Example 2

2,2,4,4-Tetramethylcyclobutane-1,3-dione was hydrogenated in thepresence of a zirconium-promoted G-69B-RS 62% nickel on kieselguhrcatalyst from Süd-Chemie using the general procedure describedpreviously.

The results of the hydrogenation of TMCB using the zirconium-promotednickel catalyst are shown in Table 2.

TABLE 2 Hydrogenation of 2,2,4,4-tetramethylcyclobutane-1,3-dione usingzirconium-promoted nickel catalyst. Example 2 Metal Ni Promoter ZrSupport kieselguhr Temperature 160° C. Pressure 32 bar TMCB % 0Ring-Open 1.5 Ketol % Cyclic Ketol % 0.3 TMPD % 0 Cis-Diol % 36.6Trans-Diol % 60.3 Conversion % 100 Selectivity % 97.8 Yield % 97.8Cis/Trans 0.6

1. A process for producing a 2,2,4,4-tetraalkylcyclobutane-1,3-diol ofFormula II, comprising contacting a2,2,4,4-tetraalkylcyclobutane-1,3-dione with hydrogen in the presence ofa promoted nickel-based catalyst under conditions of temperature andpressure sufficient to form a 2,2,4,4-tetraalkylcyclobutane-1,3-diol,

wherein each of the alkyl radicals R₁, R₂, R₃ and R₄ has, independentlyfrom each other, 1 to 8 carbon atoms and wherein less than 2 mol % ofthe 2,2,4,4-tetraalkylcyclobutane-1,3-dione is converted to ring-openproducts.
 2. The process according to claim 1, further comprisingcontacting a nickel-based catalyst with a promoter to form the promotednickel-based catalyst.
 3. The process according to claim 1, wherein thepromoted nickel-based catalyst comprises a promoter metal chosen from aGroup 4 metal.
 4. The process according to claim 3, wherein the promotercomprises zirconium.
 5. The process according to claim 1, wherein thepromoted nickel-based catalyst comprises 0.01 to 10 weight percent (wt%) promoter metal, based on the total weight of the promotednickel-based catalyst.
 6. The process according to claim 1, wherein eachof the alkyl radical radicals R₁, R₂, R₃, and R₄ has independently from1 to 4 carbon atoms.
 7. The process according to claim 1, wherein eachalkyl radical R₁, R₂, R₃, and R₄ is a methyl group.
 8. The processaccording to claim 1, wherein a non-protic solvent comprising anunsaturated hydrocarbon, a non-cyclic ester, an ether, and mixturesthereof is present.
 9. The process according to claim 8, wherein thenon-cyclic ester is chosen from isopropyl isobutyrate, isobutylpropionate, octyl acetate, isobutyl isobutyrate, isobutyl acetate, andmixtures thereof.
 10. The process according to claim 1, wherein a proticsolvent comprising one or more solvents chosen from a monohydricalcohol, a dihydric alcohol, a polyhydric alcohol, and mixtures thereofis present.
 11. The process according to claim 10, wherein the proticsolvent comprises methanol or ethylene glycol.
 12. The process accordingto claim 1, wherein the promoted nickel-based catalyst comprises akieselguhr support.
 13. The process according to claim 1, wherein thepressure is from 100 psi to 6000 psi.
 14. The process according to claim1, wherein the pressure is from 300 psi to 2000 psi.
 15. The processaccording to claim 1, wherein the temperature is from 75° C. to 250° C.16. The process according to claim 1, wherein the temperature is from130° C. to 180° C.
 17. The process according to claim 1, wherein the2,2,4,4-tetraalkylcyclobutane-1,3-diol comprisescis-2,2,4,4-tetramethylcyclobutane-1,3-diol andtrans-2,2,4,4-tetramethylcyclobutane-1,3-diol and the2,2,4,4-tetramethylcyclobutane-1,3-diol has a cis/trans molar ratio of0.4 to 1.2.
 18. The process according to claim 17, wherein the2,2,4,4-tetramethylcyclobutane-1,3-diol has a cis/trans molar ratio of0.7 to 1.0.
 19. A process for producing2,2,4,4-tetramethylcyclobutane-1,3-diol, comprising contacting2,2,4,4-tetramethylcyclobutane-1,3-dione, a promoted nickel-basedcatalyst, a non-protic solvent, and hydrogen in a hydrogenation zoneunder conditions of temperature and pressure sufficient to form2,2,4,4-tetramethylcyclobutane-1,3-diol, wherein less than 2 mol % ofthe 2,2,4,4-tetraalkylcyclobutane-1,3-dione is converted to ring-openproducts.
 20. The process according to claim 19, wherein the2,2,4,4-tetramethylcyclobutane-1,3-dione and hydrogen are continuouslyfed into the hydrogenation zone.
 21. The process according to claim 19,wherein the hydrogenation zone has a temperature from 75° C. to 250° C.22. The process according to claim 19, wherein the pressure is from 100psi to 6000 psi.
 23. The process according to claim 19, wherein thehydrogenation zone comprises a tubular reactor, a fixed bed reactor,trickle bed reactor, stirred tank reactor, continuous stirred tankreactor, or slurry reactor.
 24. The process according to claim 19,wherein the 2,2,4,4-tetramethylcyclobutane-1,3-diol has a cis/transmolar ratio of 0.4 to 1.2.
 25. A process for producing2,2,4,4-tetramethylcyclobutane-1,3-diol comprising: (a) feedingisobutyric anhydride to a pyrolysis zone, wherein the isobutyricanhydride is heated at a temperature of 350° C. to 600° C. to produce avapor effluent comprising dimethylketene, isobutyric acid, and unreactedisobutyric anhydride; (b) cooling the vapor effluent to condenseisobutyric acid and isobutyric anhydride and separating the condensatefrom the dimethylketene vapor; (c) feeding the dimethylketene vapor toan absorption zone, wherein the dimethylketene vapor is contacted with asolvent comprising an ester containing 4 to 20 carbon atoms to producean absorption zone effluent comprising a solution of dimethylketene inthe solvent; wherein the ester comprises residues of an aliphaticcarboxylic acid and an alkanol; (d) feeding the absorption zone effluentto a dimerization zone wherein the absorption zone effluent is heated ata temperature of from 70° C. to 140° C. to convert dimethylketene to2,2,4,4-tetramethylcyclobutane-1,3-dione to produce a dimerization zoneeffluent comprising a solution of2,2,4,4-tetramethylcyclobutane-1,3-dione in the solvent; and (e)contacting the 2,2,4,4-tetramethylcyclobutane-1,3-dione with hydrogen inthe presence of a promoted nickel-based catalyst under conditions oftemperature and pressure sufficient to form a2,2,4,4-tetramethylcyclobutane-1,3-diol, wherein less than 2 mol % ofthe 2,2,4,4-tetraalkylcyclobutane-1,3-dione is converted to ring-openproducts.